Cooling arrangement for thread-grinding machines

ABSTRACT

In a thread-grinding machine including a grinding table supporting a grinding wheel between two work centering spindles, of which a tail stock centering spindle is biased toward the other spindle, and further including a discharge nozzle, for a first coolant flow, at the grinding wheel support, a workpiece cooling arrangement includes a series of second discharge nozzles for a second controllable coolant flow, arranged at the grinding table in the area between the centering spindles. Valve means control the second coolant flow, and electric precision feeler means are operatively associated with the spring biased table stock centering spindle to open the valve means responsive to a predetermined axial expansion of the workpiece. The valve means include a magnet valve and a motor valve. A cooling unit is disposed in a reservoir for the second coolant, and is activated whenever the temperature of the workpiece continues to increase as determined by axial expansion of the workpiece.

United States Patent Inventor Gerhard Stade Berlin, Germany ApplNo 816,211 Filed Apr. 15. 1969 Patented July 27, 1971 Assignee Herbert Lindner G.m.b.H.

Berlin, Germany Priority July 2, 1968 Germany P 17 52 684.0

COOLING ARRANGEMENT FOR THREAD- 2/1967 Zawistowski 82/2 3,043,056 7/l9 62 Deckeretal. 51/50 Primary Examiner-Othell M. Simpson Attorney-McGlcw and Toren ABSTRACT: In a thread-grinding machine including a grinding table supporting a grinding wheel between two work centering spindles, of which a tail stock centering spindle is biased toward the other spindle, and further including a discharge nozzle, for a first coolant flow, at the grinding wheel support. a workpiece cooling arrangement includes a series of second discharge nozzles for a second controllable coolant flow, arranged at the grinding table in the area between the centering spindles. Valve means control the second coolant flow, and electric precision feeler means are operatively associated with the spring biased table stock centering spindle to open the valve means responsive to a predetermined axial expansion of the workpiece. The valve means include a magnet valve and a motor valve. A cooling unit is disposed in a reservoir for the second coolant, and is activated whenever the temperature of the workpiece continues to increase as determined by axial expansion ofthe workpiece.

coouuc ARRANGEMENT FOR THREAD-GRINDING MACHINES BACKGROUND OF THE INVENTION A known cooling arrangement for a thread-grinding machine has a main coolant line which divides into two branch lines connected to nozzles, one nozzle being located below the workpiece and the other nozzlebeing located above the workpiece. The two nozzles are oriented toward each other so that the discharging flows of coolant will meet at a common working point. Each nozzle is adjustable independently of the other. Valves are disposed in the inlet lines of the two coolant flows, to allow the desired quantity of coolant to be supplied in a unit of time to the upper and lower nozzles. Such an arrangement is shown, for example, in Swiss Pat. No. l40,2()2.

In another known cooling device for thread grinding, the two nozzles are disposed at the periphery of the grinding wheel so as to be mutually staggered, the nozzle oriented toward the grinding point being located above the grinding point, and the other nozzle being oriented toward the lower vertex of the grinding wheel. An arrangement of this type is shown, for example, in German Pat. No. 701,220.

Thread-grinding machines using two liquid coolants are disclosed, for example, in Machinery, London, Aug. 1 l, 1949, page 207 and in Wekstattstenchnik & Machinenbau, Vol. 39 (1949), pages 368 and 369. In these disclosed arrangements, two different liquids are introduced to the grinding wheel. One of the two liquids is, for instance, sulfonated or chlorinated oil impinging on the grinding wheel in a number of high velocity jets, thus forming an oil film on the peripheral surface of the wheel, and this is supposed to improve the grinding operation. The second liquid is water, and is introduced in considerable quantity under low pressure to that part of the grinding wheel covered with an oil film. After they leave the grinding point, both liquids are separated from each other again in separate tanks, or by means of centrifuges, and are then led through a heat exchanger to dissipate the heat absorbed during the grinding operation, before the liquids are returned to the grinding wheel by circulating pumps.

It is common to known cooling devices that the coolant flow or flows are introduced to the grinding point or to the grinding wheel.

As is known to those skilled in the art, changes in the length of the workpiece due to the influence of heat during machining are absorbed within the tailstock spindle by packets of cup-type springs (Industrie-Anzeiger, Essen, No. 68/69 of Aug. 28, 1953, page 869 and German Pat. No. 1,124,322.) Through the last-mentioned publication, it is also known toassociate, with an axially biased tailstock spindle, a switching feeler and a switching gear which shuts down the machine when the maximum pressure is being exceeded, and, possibly, earlier actuating a signal device. The spring-biased support of the tailstock center, usually in the form of a live center, has, for a purpose, to prevent overloading the thrust bearings. However, it is not possible to eliminate, or at least decrease, grinding inaccuracies originated due to changes in the length of the workpiece under the influence of the heat generated by the machining.

Simple cooling of the grinding point usually is inadequate for precision grinding of threads and other profiles in long spindles.

SUMMARY OF THE INVENTION This invention relates to thread-grinding machines and, more particularly, to an improved and more efficient cooling arrangement therefor.

The invention is directed to the problem of improving the grinding accuracy of threadgrinding machines, especially during grinding of long spindles. In accordance with the invention, discharge nozzles for a second, controllable flow of coolant are disposed at the grinding table in the area between the spindles or centers receiving the workpiece, of which preferably the tailstock center is supported so as to be axially biased in a known manner. The tailstock center acts upon an electric precision feeler which, in settable switching steps, actuates at least one valve in the second coolant flow and additionally activates a cooling unit. Thereby, it is possible to control or to regulate the second coolant flow, which floods the workpiece to a maximum over its entire length, as a function of occurring changes'in the length of the workpiece, thereby compensating the length change in a direction toward zero. The grinding accuracy attainable is substantially improved, and lies within tolerances hitherto not attainable. The switching points are adjusted in accordance with the tolerance of the workpiece.

In one embodiment of the invention, the electric precision feeler opens, in a first switching position, a magnet valve having a constant flow cross section, and switches on the cooling unit, by means of a make-before-break contact in a secondswitching position, in addition to maintaining the magnet valve operated.

In accordance with another embodiment of the invention, the electric precision feeler actuates a motor valve whose flow cross section can be regulated, and switches on a cooling unit at a maximum flow with acontinued increase in the length of the workpiece. In this embodiment, the electric precision feeler may function in accordance with the principle of an inductive measuring instrument, such as is known per se.

The electric precision feeler may, in accordance with another embodiment of the invention, actuate a magnet valve and a controllable motor valve, each associated with a respective pump which respectively pump uncooled and cooled coolant from two respective chambers of the coolant tank into a common main connected to the discharge nozzles.

in all of these embodiments, a thermostat, adjustable to a minimum temperature of the cooling unit, may serve for deactivating the cooler unit.

Advantageously, a distributor line is arranged at the grinding table, and at least partially flexible tubular lines, approximately equally spaced, branch off from this distributor line. The branch lines are equipped with the discharge nozzles, which can be oriented toward the workpiece over the length of the latter. By this'simple means, there is attained the result that the workpiece, regardless of the position of the respective grinding point, can be flooded with coolant and kept at a constant length in accordance with the heat expansion which is to be compensated. It is expedient if the tubular lines branching from the distributor lines are adjustable individually with respect to their flow-through cross section. This adjustment may be made either manually or mechanically.

This makes it possible to adjust the heat dissipation in the various cooling zones differently, if this may be of advantage in a particular case. Generally, the adjustment depends upon the length of the workpiece which is to be machined.

An object of the invention is to provide improved cooling arrangement for a thread-grinding machine.

Another object of the invention is to provide such a cooling arrangement in which, in addition to a first coolant flow directed at a thread-grinding wheel, a second coolant flow is directed along substantially the entire length of the workpiece.

A further object of the invention is to provide such a cooling arrangement in which flow of the second coolant is controlled in accordance with a heat expansion of the workpiece during grinding.

Another object of the invention is to provide such a cooling arrangement in which, responsive to a continued expansion of the workpiece, a cooling unit, for cooling the second coolant, is activated. I

A further object of the invention is to provide such an arrangement including a thermostat, adjustable to a minimum temperature, serving to deactivate the cooling unit.

Another object of the invention is to provide such an arrangement including a distributor line extending along the grinding table, at least partially flexible tubular lines, approxiniately equally spaced, branching off from the distributor lines, and discharge nozzles connected to the respective distributor lines and which can be oriented toward the workpiece over the entire length of the latter.

A further object-of the invention is to provide such a cooling arrangement in which the discharge of the individual nozzles can be adjusted independently of all other nozzles, either manually or mechanically.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings.

BRIEF DESCRlPTlON OF THE DRAWINGS In the Drawings:

FIG. 1 is somewhat schematic elevation view, partly in sec tion, of a thread-grinding machine provided with the cooling arrangement embodying the invention;

FIG. 2 is an enlarged side elevation view of the machine shown in FlG.1;

FIG. 3 is a schematic view ofa modified form oftlie cooling arrangement, in which a motor valve controls flow of the second coolant; and

HO. 4 is a schematic view ofa modified form of the cooling arrangement, involving a mixing valve arrangement.

DETAILED DESCRlPTiON OF THE PREFERRED EMBODIMENTS Referring first to FlGS. l and 2, the thread--grinding machine includes a bed i, a grinding table 2, a workpiece spindle box 3 having a spindle center 4, a tailstock 5 with a tailstock spindle center 6, and a grinding wheel support 7 carrying a profiled grinding wheel 8. The workpiece 9 is a long threaded spindle whose thread is being ground, and which is chucked between the centers 4 and 6. The workpiece receives its rotary motion through a driver and a dog, neither of which is shown as they form no part of the present invention. At the grinding wheel support, there is arranged a coolant discharge nozzle 10 which is oriented toward grinding wheel 8, and hence toward the respective grinding point when the workpiece is led past the grinding wheel due to the back and lorth motion of the grinding table. This discharge nozzle, which is provided for the usual coolant flow, communicates with a pump 13 through a conduit 1i having a shutoff valve 12 built thereinto. Pump 13 is operatively associated with a coolant tank 14.

Tailstock S has a spindle center which is supported so as to be spring biased in an axial direction toward the centering spindle 4, and tailstocks of this type are already known so therefore the tailstock has been shown schematically only. The axially movable spindle sleeve is illustrated at 15, as being engaged by a compression spring id whose preloading is settable by a handwheel 17 through the medium ofa threaded spiridle 18.

A clamping ring 19, attached to spindle sleeve 15, carries a measuring rod 20 which cooperates with the feeler pin 21 of an electric precision feeler .22 having two switch positions illustrated, respectively, at 23 and 24. Precision feeler 22 has contacts 25, 26 and 27, of which the central contact 27 is a make-before-break contact. Control conductors 28 connect precision feeler 22 to amplifier 29, which is connected through conductors indicated at 30 to a magnet valve 31. This magnet valve, when opened, has a constant flow cross section for the second coolant flow which is pumped to magnet valve 31 through conduit line 30 by pump 32.

A flexible conduit 34 connects magnet valve 31 to a conduit 35 which is stationarily disposed within grinding table 2 and which, in turn, communicates with the distributor line 36 stationarily disposed on the grinding table. A plurality of at least partially flexible tubular lines 37 are approximately equally spaced along distributor line 36, these tubular lines 37 branching from distributor line 36. Respective discharge nozzles 38 are provided for each flexible tubular line 37, and these discharge nozzles are oriented toward workpiece 9 over the entire length of the latter. Tubular lines 37 are provided with joints 39, for adjustment thereof, and with control valves 40 by means of which the flow through each nozzle 38 may be adjusted.

The first coolant flow, illustrated in FIG. 2, is indicated at 41, and the second coolant flow at 42. Both coolant flows are caught in trough 43 of grinding table 2, from which they drain as indicated by the arrow 44. The drained coolant reaches return line 45. and is thence delivered back to coolant tank 14.

Located in coolant tank 14 are cooling unit 46 and a thermostat 457, which controls cooling unit 46 by means of an electric line 48. An electric line 49 connects cooling unit 46 with amplifier 2). Cooling unit 46 is activated, in addition to magnet valve 31, after the make-before-break contact 26 has moved to the switch position 24, and the cooling unit is dcenergized by thermostat 47 at a selected minimum temperature of the coolant in tank 14.

In the embodiment of the invention shown in FIG. 3, an inductive-type electric precision feeler 22a is used, and permits a continual field regulation ofa motor valve 31a whose motor M is a variable speed motor. At maximum flow with continued increase in the length of the workpiece, cooling unit 46 is activated through a line 49 branching from amplifier 29.

in a third embodiment of the invention, shown in H0. 4, a mixing valve arrangement includes magnet valve 31 and adjustable motor valve 310. Through respective lines 30 and 30a, magnet valve 31 and adjustable motor valve 31a'are connected to amplifier 29. In turn, amplifier 29 is connected by lines 28 to the inductive precision feeler 22a.

There is operatlvely associated with magnet valve 31 a pump 32 connected to valve 31 through a conduit 33, and a pump 32, associated with motor valve 30a is connected to the latter through a conduit 33a. The coolant tank has a built-in separating wall 50 with an overflow, this dividing the coolant tank into two chambers 14a and 14b. The uncooled coolant is in chamber 140, and the coolant cooled by cooling unit 46 is in chamber 14b. The mixed coolant flows through line 34, connected to the outlets of magnet valve 31 and motor valve 31a, to discharge nozzles 38 for the second coolant flow 42. The coolant pump 13 in cooled chamber 14b of the coolant tank supplies the discharge nozzle 10, for the first coolant, which is oriented toward the grinding point.

In each embodiment of the invention, it is the second, controlled coolant flow 42 which makes it possible to compensate continually for changes in the length of the workpiece beyond the tolerances. As a result, long-threaded spindles can be ground with extreme accuracy.

What 1 claim is:

T. in thread-grinding machine of the type including a workpiece spindle box and a tailstock having centering spindles for a workpiece, a grinding table supporting a grinding wheel between the spindles, and a first discharge nozzle, for a first coolant flow, at the grinding wheel support: a workpiece cooling arrangement comprising, in combination, second discharge nozzles for a second, controllable coolant flow, arranged at the grinding table in the area between said centering spindles; said tailstock centering spindle being biased axially toward said spindle box; valve means controlling said second coolant flow; and precision feeler means controlling said valve means and operable by axial displacement of said tailstock centering spindle; said feeler means operating, responsive to a predetermined axial expansion of the workpiece, to open said valve means for flow of said second coolant to said second nozzles.

2. in a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 1, in which said precision feeler-means is an electric precision feeler which has settable switching positions.

3. in a thread-grinding machine, rangement, as claimed in claim 2, operable to cool the second coolant.

a workpiece cooling arincluding a cooling unit 4. [n a thread-grinding machine, a workpiece cooling ar-' rangement, as claimed in claim 3, including a magnet valve having a constant flow cross section; said electric precision feeler have a make-before-break contact which, in a first switch position, activates said magnet valve to the open position and, in a second-switching position, additional to said first-switching position, activates said cooling unit.

5. in a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 3, including a motor operated valve having a variable flow cross section which can be adjusted; said electric precision feeler controlling said motor operated valve.

6. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 5, in which said precision feeler activates said cooling unit at maximum flow of said motor operated valve, with continued increase in the length of the workpiece.

7. in a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 3, in which said valve means comprises a mixing valve arrangement including magnet valve and controllable motor operated valve; a coolant reservoir; means dividing said coolant reservoir into two chambers, one having said cooling unit disposed therein; a first pump means supplying coolant from the other chamber to said magnet valve; a second pump means supplying coolant from said one chamber to said motor-operated valve; and a common output conduit connecting the outlets of-said magnet valve and said motor-operated valve to said second discharge nozzles.

8. ln a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 3, including a thermostat subjected to the second coolant and settable to a minimum temperature thereabove; said thermostat deactivating said cooling unit when the second coolant has said minimum temperature.

9. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 3, including a distributor conduit at said grinding table; a plurality of at least partially flexible tubular conduits connected to said distributor conduit at approximately equally spaced intervals; said second discharge nozzles comprising respective nozzles connected to each of said flexible conduits, said second discharge nozzles being orientable toward the workpiece over the entire length of the latter.

[0. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 9, including respective means operable to regulate the flow through each flexible conduit independently of each other flexible conduit. 

1. In thread-grinding machine of the type including a workpiece spindle box and a tailstock having centering spindles for a workpiece, a grinding table supporting a grinding wheel between the spindles, and a first discharge nozzle, for a first coolant flow, at the grinding wheel support: a workpiece cooling arrangement comprising, in combination, second discharge nozzles for a second, controllable coolant flow, arranged at the grinding table in the area between said centering spindles; said tailstock centering spindle being biased axially toward said spindle box; valve means controlling said second coolant flow; and precision feeler means controlling said valve means and operable by axial displacement of said tailstock centering spindle; said feeler means operating, responsive to a predetermined axial expansion of the workpiece, to open said valve means for flow of said second coolant to said second nozzles.
 2. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 1, in which said precision feeler means is an electric precision feeler which has settable switching positions.
 3. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 2, including a cooling unit operable to cool the second coolant.
 4. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 3, including a magnet valve having a constant flow cross section; said electric precision feeler have a make-before-break contact which, in a first switch position, activates said magnet valve to the open position and, in a second-switching position, additional to said first-switching position, activates said cooling unit.
 5. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 3, including a motor operated valve having a variable flow cross section which can be adjusted; said electric precision feeler controlling said motor operated valve.
 6. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 5, in which said precision feeler activates said cooling unit at maximum flow of said motor operated valve, with continued increase in the length of the workpiece.
 7. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 3, in which said valve means comprises a mixing valve arrangement including magnet valve and controllable motor operated valve; a coolant reservoir; means dividing said coolant reservoir into two chambers, one having said cooling unit disposed therein; a first pump means supplying coolant from the other chamber to said magnet valve; a second pump means supplying coolant from said one chamber to said motor-operated valve; and a common output conduit connecting the outlets of said magnet valve and said motor-operated valve to said second discharge nozzles.
 8. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 3, including a thermostat subjected to the second coolant and settable to a minimum temperature thereabove; said thermostat deactivating said cooling unit when the second coolant has said minimum temperature.
 9. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 3, including a distributor conduit at said grinding table; a plurality of at least partially flexible tubular conduits connected to said distributor conduit at approximately equally spaced intervals; said second discharge nozzles comprising respective nozzles connected to each of said flexible conduits, said second discharge nozzles being orientable toward the workpiece over the entire length of the latter.
 10. In a thread-grinding machine, a workpiece cooling arrangement, as claimed in claim 9, including respective means operable to regulate the flow through each flexible conduit independently of each other flexible conduit. 